Anthracyclines form one of the largest families of naturally occurring bioactive compounds. Several members of this family have shown to be clinically effective anti-neoplastic agents. These include, for example, daunorubicin, doxorubicin, idarubicin, epirubicin, pirarubicin, zorubicin, aclarubicin, and carminomycin. For instance, these compounds have shown to be useful in the treatment of breast carcinoma, acute lymphocytic and non-lymphocytic leukemia, chronic lymphocytic leukemia, non-Hodgkin's lymphoma, and other solid cancerous tumors.
Carminomycin (in the form of Formula (1)) is a well-known anthracyclin antibiotic that is used both in defined clinical applications and as a starting material for synthesis of multiple 4-modified anthracylins, and in particular, idarubicin (see for example, U.S. Pat. No. 7,053,191, the contents of which is hereby incorporated by reference herein in its entirety).
Microbiological production of carminomycin is complicated by a very low productivity of the known strains of microorganisms, at the level of 0.1-0.3 g/L. Up until the present, the synthetic method of preparing carminomycin has been very protracted (involving 10-12 chemical stages) and expensive. In the previously described methods of 4-methoxy group demethylation, the substrate was daunorubicinone because there had been no known methods of 4-methoxy group demethylation without breaking of the C-7 glycoside bond. The most common method of the 4-methoxy group demethylation involves treatment of the daunorubicinone with a strong Lewis acid, AlCl3, in inert solvents such as chlorinated hydrocarbons (ex. dichloromethane) at boiling temperature. In an attempt to conduct the same synthesis with daunorubicin, the daunosamine glycoside bond is severed, and the anthracyclin nucleus is destroyed.